The present invention relates generally to visual display systems and more particularly to miniature display devices which use a beamsplitter to generate a magnified virtual image of the image formed by the miniature display device.
Miniature display devices may be used in a number of ways, although they are particularly well suited for use in a head-mounted display. Head-mounted displays which are mounted on the head of a viewer have typically been bulky and large. These displays often use small cathode ray tubes to project an image toward a viewer's eye. Numerous head-mounted displays are known in the art. See, for example, the book Head-Mounted Displays, by James E. Melzer, and Kirk Moffitt, which is published by McGraw-Hill. These displays are sometimes also referred to as displays which are brought to the head (of the viewer).
Certain head-mounted displays use a liquid crystal technology to provide a visual display rather than using cathode ray tubes. For example, U.S. Pat. No. 5,596,451 describes a miniature image generator which uses a liquid crystal display device in conjunction with magnifying mirrors to generate an image which may be used with a head-mounted display. Examples of liquid crystal display devices which may be used in this context may be found in U.S. Pat. Nos. 5,566,010 and 5,426,526.
While liquid crystal display devices in head-mounted displays provide certain advantages in terms of the weight and bulk of the resulting display, these displays are often poorly suited to displaying high quality images because of the short optical paths required by a small enclosure which houses the head-mounted display. For example, these displays use conventional beamsplitters which have limited angles of acceptance, which tends to make the display non-uniform across the entire image. Thus, while head-mounted display devices which use liquid crystal displays rather than CRT's are smaller and lighter, they do not provide the performance advantages of CRT's. Thus, it is desirable to provide a head-mounted display which is both lightweight and small and yet provides high quality performance even for color video data at fast frame rates.